How to Treat Green Water
Pond Care
Green water normally appears in all ponds during early spring before the other plants have had a chance to grow and compete. This also happens with freshly cleaned and filled ponds, rich in mineral salts. This is a natural, healthy process. DO NOT use algaecides and DO NOT flush and refill your pond, or the “curing” process will have to start all over again.
To minimize green water:
Only in extreme cases should you do a partial water change or try water clarifying chemicals. First, try temporarily shading your pond with planking or other cover. Remember, all green plants, including algae, are beneficial in the garden pond. They all absorb nutrients, convert them to new plant tissue, and give off oxygen as a by-product. This is known as photosynthesis. The algae on the sides of your pond provide 70-80% of the oxygen your fish need to survive. A balanced water garden contains relatively clear water yet allows some algae to exist for the benefit of the other pond inhabitants. In a healthy pond, you can usually see your hand (or fish) about 12” below the water surface. Anything below the 12” mark will not be clearly visible.
So be patient. With time and proper balancing practices, your pond will clear. Meanwhile, remember that green water is not unhealthy for plants or fish. It is just a natural part of the spring pond cycle.
To minimize green water:
- Make sure the pond has a good balance of plants, fish, and scavengers. When in doubt, add plants that compete for nutrients and shade the surface (submerged aquatics, floaters, and water lilies).
- Add beneficial bacteria to speed up balancing and reduce the green water period.
- Stop feeding the fish (or at least restrict to 1-2 times per week and only what they eat in 5 minutes).
- Check the pH: If it is above 8.5, plants cannot effectively take in nutrients to compete with the algae.
- Add or improve filtration.
Only in extreme cases should you do a partial water change or try water clarifying chemicals. First, try temporarily shading your pond with planking or other cover. Remember, all green plants, including algae, are beneficial in the garden pond. They all absorb nutrients, convert them to new plant tissue, and give off oxygen as a by-product. This is known as photosynthesis. The algae on the sides of your pond provide 70-80% of the oxygen your fish need to survive. A balanced water garden contains relatively clear water yet allows some algae to exist for the benefit of the other pond inhabitants. In a healthy pond, you can usually see your hand (or fish) about 12” below the water surface. Anything below the 12” mark will not be clearly visible.
So be patient. With time and proper balancing practices, your pond will clear. Meanwhile, remember that green water is not unhealthy for plants or fish. It is just a natural part of the spring pond cycle.